1. Field Of The Invention
The invention relates to a process for the production of thiotetronic acid. 2. Prior Art
It has been reported that thiotetronic acid has been used as an intermediate product for the production of (+) thiolactomycin, an antibiotic having a broad effective spectrum Tetrahedron Letters, Vol. 25, No. 46, pp. 5243 to 5246, (1984) discloses that the dimethyl homologue compound of thiotetronic acid can be used to make (.+-.)-thiolactomycin, an antibiotic having a broad effective spectrum, and the diethyl homologue compound of thiotetronic acid can be used to make thiotetromycin. Accordingly, the Tetrahedron Letters letter would cause one skilled in the art to recognize the possible use of thiotetronic acid for the production of a thiolactomycin derivative.
From E. Benary, Chemische Berichte 46, 2103 (1913), it is known to produce thiotetronic acid starting out from acetylthioglycoyl chloride as a result of reaction thereof with sodium malonic ester and subsequently ring closure and water treatment D. B. Macierewicz, Rocz. Chem. 47, 1735, (1973), reproduced the reaction of E. Benary and obtained at the same time thiotetronic acid at a yield of 30.3 percent, related to the acetylthioglycoyl chloride used. Another possibility for synthesis is set out in J. Z. Mortensen et al., Tetrahedron, 27, 3839, (1971). Starting out from 2,4-dibromothiophene, the thiotetronic acid is obtained in a yield of 46.2 percent by way of three steps as a result of reaction with butyl lithium and t-butylperbenzoate.
In the case of all of the above-identified traditional syntheses, the yields thereof are much too low for a technical or commercial process. Moreover, the processes are hindered by cumbersomeness, expensive educts and by reagents that are difficult to handle.